Performance on different host plants of an alien and an indigenous Bemisia tabaci from China

The capacity of the Middle East‐Asia Minor 1 putative species of the whitefly Bemisia tabaci (Gennadius) species complex, commonly referred to as the ‘B biotype’, to invade has often been linked to its presumed wider host range than the indigenous competitors. To determine whether this alien putative species and the indigenous Asia II 1 whitefly putative species, commonly referred to as the ‘ZHJ2 biotype’, differ in their ability to use different host plants, we compared their development, survival and reproduction on eight crop species/cultivars that are commonly cultivated in Zhejiang, China. Of the eight host plants tested, B performed substantially better than ZHJ2 on squash, tomato and tobacco, B and ZHJ2 preformed equally well on cotton and sweet potato, while ZHJ2 performed better than B on kidney bean and pepper. These results indicate that while B generally has a wider host range than many indigenous B. tabaci, an indigenous B. tabaci can perform as well as or better on some host plants. These results combined with the cropping patterns in Zhejiang suggested that the differential capacity to use various host plants between whitefly species is important in mediating the process of invasion by an alien whitefly species.     

Competition between Quercus petraea and Carpinus betulus in an ancient wood in England: seedling survivorship

Abstract. Age structures of populations of canopy trees in Wormley Wood are consistent with reports that successional change is occurring, with Carpinus betulus replacing Quercus petraea as the dominant species. TWINSPAN analysis of data from a vegetation survey identifies three communities (described in earlier work), the ‘Bracken’, ‘Bramble’, and‘Bareground’ societies, characterized by increasing prominence of C. betulus and loss of species diversity. An experiment was set up in which C. betulus, Q. petraea and Betula pendula seedlings were explanted into each of the communities. Survival of seedlings was monitored over 860 days and differences investigated. Cohort survivorship differed between species and sites. C. betulus seedlings survived longer than Q. petraea in Bracken and Bramble communities. Species- and site-specific variation in the types and effects of herbivory were found. Herbivory did not appear to be a critical factor in the survival of Q. petraea seedlings. The photosynthetic light response of the seedling species was measured in the field. The light compensation point for Q. petraea seedlings (77 μmol photon m^-2 s^-1) is higher than the maximum available light under the main tree canopies in the wood. In contrast, seedlings of C. betulus have a lower light compensation point (15 μmol photon m² s^-1) and the mature tree casts a deeper shade than Q. petraea. It is suggested that the invasion of the canopy by C. betulus, following the cessation of coppicing, is creating light levels too low for Q. petraea seedling banks to persist.     

苋科(广义)入侵植物墙生藜在中国的新记录

外来物种的归化和入侵对全球环境和社会发展造成了严重影响，已成为当今各国生物多样性管理和生态保护中所面临的全球性问题。我国是遭受外来入侵危害最为严重的国家之一，在外来物种入侵的预警、管理和治理等方面形势严峻。基于野外调查和文献研究，该文报道了苋科(广义)入侵植物墙生藜[Chenopodiastrum murale(L.) S. Fuentes, Uotila&Borsch]在中国的新记录。墙生藜原产于地中海地区，现已扩散到欧洲、美洲、非洲和大洋洲的40多个国家，是一种危害较大的外来入侵植物，同时也是我国海关和检验检疫部门明确规定禁止入境的检疫性有害生物，现于云南省昆明市呈贡区发现该外来入侵植物。该文对其形态特征进行了详细描述，简要介绍了其分类历史，并提供了可供鉴定比对的野外生态照片；此外，对墙生藜可能的传入途径进行了分析，对其危害和风险作了简要评估。该物种的新发现说明我国外来入侵生物的本底调查还存在不足。     

Invasion status and impacts of parthenium weed (Parthenium hysterophorus) in West-Central region of Bhutan

Parthenium weed (Parthenium hysterophorus L.) is an invasive alien plant species that is spreading rapidly all over the world. With globalization and climate change, it will continue to spread, posing threats to agriculture, biodiversity and the environment. To determine its invasion and impacts in Bhutan, an investigation was undertaken in West-Central Bhutan using a questionnaire survey, complemented by MaxEnt modelling. Most farmers (19–30%) recall having seen parthenium for the last 11–15 years, or more. Infestations of parthenium differed significantly (P?<?0.05) across three districts for dryland, orchards, fallow land and pastures, but not in rice fields and on roadsides. The most intensely invaded land types were fallow land, pastures, and roadsides, with farmers perceiving it as ‘somewhat common’(score?~?3) and ‘common’ (score?~?4) weed. Farmers’ perceptions of the invasiveness of parthenium weed were high at 77% (Wangdue), 80% (Punakha), and 88% (Tsirang), considering it as at least ‘somewhat invasive’, or higher. Only 13–25% of respondents scored the weed as ‘highly invasive’. Parthenium invasion significantly (P?<?0.01 to 0.001) escalated the cost of production, reduced fodder quality, supressed native species and caused allergies to the locals in the study districts. Further, MaxEnt modelling of parthenium distribution was undertaken, using the parthenium presence-only data and bioclimatic variables, under 2 CO₂ emission scenarios of the Intergovernmental Panel on Climate Change (IPCC), i.e. Representative Concentration Pathways (RCP2.6 and 8.5). The projections showed discernible spatial changes in climate suitability over 2070, mostly in the mid- and high-altitude zones, indicating aggressive incursion into Bhutan’s important agro-ecological landscapes. The findings, highlight the urgent need to initiate parthenium management strategies for food production and natural resources.

     

The global invasion success of Central European plants is related to distribution characteristics in their native range and species traits

Aim Determining which traits predispose a species to become invasive is a fundamental question of invasion ecology, but traits affect invasiveness in concert with other factors that need to be controlled for. Here, we explore the relative effects of biological traits of plant species and their distributional characteristics in the native range on invasion success at two stages of invasion. Location Czech Republic (for native species); and the world (for alien species). Methods The source pool of 1218 species of seed plants native to Central Europe was derived from the flora of the Czech Republic, and their occurrence in 706 alien floras all over the world was recorded, distinguishing whether they were listed as an ‘alien’ or a ‘weed’ in the latest version of Randall’s ‘Global compendium of weeds’ database. The latter type of occurrence was considered to indicate species ability to invade and cause economic impact, i.e. a more advanced stage of invasion. Using the statistical technique of regression trees, we tested whether 19 biological traits and five distributional characteristics of the species in their native range can be used to predict species success in two stages of invasion. Results The probability of a species becoming alien outside its native distribution range is determined by the size of its native range, and its tolerance of a wide range of climates acquired in the region of origin. Biological traits play only an indirect role at this stage of invasion via determining the size of the native range. However, the ability of species to become a weed is determined not only by the above characteristics of native distribution, but also directly by biological traits (life form and strategy, early flowering, tall stature, generative reproduction, number of ploidy levels and opportunistic dispersal by a number of vectors). Species phylogenetic relatedness plays only a minor role; it is more important at the lowest taxonomic levels and at the later stage of invasion. Main conclusion The global success of Central European species as ‘weeds’ is determined by their distributional characteristics in the native ranges and by biological traits, but the relative importance of these determinants depends on the stage of invasion. Species which have large native ranges and are common within these ranges should be paid increased attention upon introductions, and the above biological traits should be taken into account in screening systems applied to evaluate deliberate introductions of alien plants to new regions.     

Functional traits,growth patterns,and litter dynamics of invasive alien and co-occurring native shrub species of chir pine forest in the central Himalaya,India

Across the continents, plant invasion is identified as one of the main threats to ecosystem functioning and stability. The main objective of this research was to evaluate the differences in the functional traits between invasive alien (Ageratina adenophora (Spreng.) and Lantana camara L.) and native (Berberis asiatica Roxb. Ex DC., Pyracantha crenulata (D. Don.) M. Roemer and Rubus ellipticus Sm.) shrub species of chir pine (Pinus roxburghii Sarg.) forest in the central Himalaya. Three 0.5 hectare chir pine forest stands were selected and individuals of similar diameter were tagged for comparative studies of leaf traits, growth pattern, and biomass accumulation in structural organs of each invasive alien and native species. Our one-way ANOVA and Tukey’s post hoc test results showed that both the invasive alien species have significantly (p?<?0.05) higher SLA, LWC, total chlorophyll content, foliar nutrient (N and P), RGR, LMR, SMR, nutrient uptake, and nutrient use efficiencies than native species. Leaf litter decomposition rate and nutrient release were also significantly (p?<?0.05) higher in both the invasive alien species. Native species, R. ellipticus, shared some of the traits, such as leaf area, chlorophyll content, RGR, LAR, LMR, and nutrient uptake efficiency with invasive alien species. The majority of traits differed among invasive alien and native species, implying that the success of invasive alien species is best described by being functionally distinct from native species. These findings indicate that invasive alien species had advanced functional traits which may be playing an important role in a rapid spread in the central Himalaya.

     

Invasion trajectory of alien trees: the role of introduction pathway and planting history

Global change is driving a massive rearrangement of the world's biota. Trajectories of distributional shifts are shaped by species traits, the recipient environment and driving forces with many of the driving forces directly due to human activities. The relative importance of each in determining the distributions of introduced species is poorly understood. We consider 11 Australian Acacia species introduced to South Africa for different reasons (commercial forestry, dune stabilization and ornamentation) to determine how features of the introduction pathway have shaped their invasion history. Projections from species distribution models (SDMs) were developed to assess how the reason for introduction influences the similarity between climatic envelopes in native and alien ranges. A lattice model for an idealized invasion was developed to assess the relative contribution of intrinsic traits and introduction dynamics on the abundance and extent over the course of simulated invasions. SDMs show that alien populations of ornamental species in South Africa occupy substantially different climate space from their native ranges, whereas species introduced for forestry occupy a similar climate space in native and introduced ranges. This may partly explain the slow spread rates observed for some alien ornamental plants. Such mismatches are likely to become less pronounced with the current drive towards ‘eco gardens’ resulting in more introductions of ornamental species with a close climate match between native and newly introduced regions. The results from the lattice model showed that the conditions associated with the introduction pathway (especially introduction pressure) dominate early invasion dynamics. The placement of introduction foci in urban areas limited the extent and abundance of invasive populations. Features of introduction events appear to initially mask the influence of intrinsic species traits on invasions and help to explain the relative success of species introduced for different purposes. Introduction dynamics therefore can have long‐lasting influences on the outcomes of species redistributions, and must be explicitly considered in management plans.     

Biological invasion on an oceanic island mountain: Do alien plant species have wider ecological ranges than native species?

Abstract. Spatial distribution patterns of alien plant species were compared with those of native species on a windward slope of Mt. Haleakala (3055 m). Oceanic islands are considered susceptible to biological invasion, and this study numerically tested this circumstantial evidence with the following questions: Are all habitats equally susceptible; and, do successful invaders have wider realized niches than natives? The mountain slope consists of three distinct altitudinal bioclimatic zones (hot moist lowland, wet montane cloud, and cool arid high-altitude zones). Ordination indicated that alien species' ranges and population expansions were clustered in the lowland and high-altitude zones. The lowland zone had been subjected to natural canopy dieback, and the high-altitude zone to grazing by domestic and feral ungulates. By contrast, the montane cloud forest was relatively intact in terms of number and cover of native species. Thus, susceptibility to alien invasion clearly differed among zones, and the primary causes seemed to be the obvious disturbance factors. The mean ecological range along the altitude-rainfall gradient was significantly (P < 0.05) greater for native than for alien species in most life-form groups. The reasons for the greater number of climate generalists among the natives vs. the range-restricted aliens appear to be related to: (1) the pre-alien condition with a depauperate flora which allowed for ‘ecological release’ of successful native colonizers, and (2) the climatic pre-adaptation of alien invaders which restricts them from penetrating over a broader spectrum of climatic zones in a floristic matrix subjected to increasing interspecific competition.     

广西及越南农业外来有害生物入侵现状

【背景】广西地理环境独特,与越南水陆相连,气候、作物等条件相似,边境贸易往来频繁,致使其成为我国遭受外来有害生物入侵最严重的地区之一。【方法】通过本底调查,分析总结了广西农业外来有害生物入侵的现状。【结果】广西主要入侵动物26种,入侵微生物18种,入侵植物21种,高风险入侵物种包括辣椒实蝇、木薯绵粉蚧、扶桑绵粉蚧、稻水象甲、黄瓜绿斑驳花叶病毒等;来自越南的潜在危险性有害生物共38种。【结论与意义】广西受外来有害生物入侵的风险加剧,并有进一步扩散蔓延的趋势。提出应对入侵生物的综合防控对策,为广西外来入侵有害生物的防控提供参考。     

The diet of native and invasive fish species along the eastern Mediterranean coast (Osteichthyes)

The opening of the Suez Canal in 1869 enabled the invasion of more than 100 alien fish species into the Mediterranean. The aim of the present study was to compare the diet of native and alien fish species and to identify possibly shared food resources. We examined the diet composition of 13 of the most abundant fish species (6 alien, 7 native) on shallow soft bottom off southern Israel. All 13 species are omnivorous/carnivorous. The native fish exhibited a wider diversity of food types than the aliens. Alien fish prey upon and are preyed by native species as well as by other alien fish. A high level of diet overlap was found among some species, the aliens Saurida lessepsianus and Scomberomorus commerson overlapped with the native Synodus saurus; and the alien Nemipterus randalli with the native species Pagrus caeruleostictus, Lithognathus mormyrus and Pagellus erythrinus. The identified diet overlap is discussed, and the possibility of competitive interactions between these species is considered.     

Island biogeography as a test of reproductive interference

Theoretical studies have predicted that reproductive interference must exclude either of the interacting species, but no testing of this prediction has ever been reported for natural populations. This study surveyed the distribution patterns of herbaceous Veronica plants, including one native and three alien species, to test whether the invasion of the alien species exerting reproductive interference excluded the native species. Results showed that the native species was repeatedly excluded from islands where an alien species invaded, exerting reproductive interference, and that other alien species had no significant effect on the native population survival. This survey also demonstrated that the native species altered its habitat from the ground to stone walls on the mainland where the alien species had been predominant. In the mainland populations, the fruit morphology differed from that of the islands, and the morphology in the mainland population seemed suitable for seed dispersion by ants at a stone wall habitat. We also surveyed the genetic differentiation among populations, the results of which did not support the native species genetically differentiated between mainland and island populations before the alien species invasion. These results strongly suggest that the reproductive interference excluded the recipient species at the population level and facilitated the habitat change. Additionally, results indicated that a series of field surveys of islands close to the mainland can be a powerful tool to test the ecological importance of reproductive interference.     

Predicting plant invasions under climate change: are species distribution models validated by field trials?

Climate change may facilitate alien species invasion into new areas, particularly for species from warm native ranges introduced into areas currently marginal for temperature. Although conclusions from modelling approaches and experimental studies are generally similar, combining the two approaches has rarely occurred. The aim of this study was to validate species distribution models by conducting field trials in sites of differing suitability as predicted by the models, thus increasing confidence in their ability to assess invasion risk. Three recently naturalized alien plants in New Zealand were used as study species (Archontophoenix cunninghamiana, Psidium guajava and Schefflera actinophylla): they originate from warm native ranges, are woody bird‐dispersed species and of concern as potential weeds. Seedlings were grown in six sites across the country, differing both in climate and suitability (as predicted by the species distribution models). Seedling growth and survival were recorded over two summers and one or two winter seasons, and temperature and precipitation were monitored hourly at each site. Additionally, alien seedling performances were compared to those of closely related native species (Rhopalostylis sapida, Lophomyrtus bullata and Schefflera digitata). Furthermore, half of the seedlings were sprayed with pesticide, to investigate whether enemy release may influence performance. The results showed large differences in growth and survival of the alien species among the six sites. In the more suitable sites, performance was frequently higher compared to the native species. Leaf damage from invertebrate herbivory was low for both alien and native seedlings, with little evidence that the alien species should have an advantage over the native species because of enemy release. Correlations between performance in the field and predicted suitability of species distribution models were generally high. The projected increase in minimum temperature and reduced frosts with climate change may provide more suitable habitats and enable the spread of these species.     

Trophic consequences of non‐native species for commercial fish in a backwater bay of the Three Gorges Reservoir,Southwest China

Trophic niche overlap in native and alien fish species can lead to competitive interactions whereby non‐native fishes outcompete indigenous individuals and eventually affect the viability of natural populations. The species Erythroculter mongolicus and Erythroculter ilishaeformis (belonging to the Culterinae), which are two commercially important fish species in the backwater bay of the Pengxi River in the Three Gorges Reservoir (TGR), were threatened by competition from the non‐native Coilia ectenes (lake anchovy). The latter is an alien species introduced into the lower reaches of the Yangtze River in China and now widespread in the TGR. The trophic consequences of non‐native lake anchovy invasion for E. mongolicus and E. ilishaeformis were assessed using stable isotope analysis (δ¹³C and δ¹⁵N) and associated metrics including the isotopic niche, measured as the standard ellipse area. The trophic niche of native E. mongolicus had little overlap (<15%) with the alien fish species and was significantly reduced in size after invasion by lake anchovy. This suggests that E. mongolicus shifted to a more specialized diet after invasion by lake anchovy. In contrast, the trophic niche overlap of native fish E. ilishaeformis with the alien fish species was larger (>50%) and the niche was obviously increased, implying that fish in this species exploited a wider dietary base to maintain their energetic requirements. Thus, marked changes for the native E. mongolicus and E. ilishaeformis were detected as the trophic consequences of invasion of non‐native lake anchovy.     

Integrating transport pressure data and species distribution models to estimate invasion risk for alien stowaways

The number of alien species transported as stowaways is steadily increasing and new approaches are urgently needed to tackle this emerging invasion pathway. We introduce a general framework for identifying high‐risk transport pathways and receiving sites for alien species that are unintentionally transported via goods and services. This approach combines the probability of species arrival at transport hubs with the likelihood that the environment in the new region can sustain populations of that species. We illustrate our approach using a case study of the Asian black‐spined toad Duttaphrynus melanostictus in Australia, a species that is of significant biosecurity concern in Australasia, Indonesia, and Madagascar. A correlative model fitted to occurrence data from the native geographic range of D. melanostictus predicted high environmental suitability at locations where the species has established alien populations globally. Applying the model to Australia revealed that transport hubs with the highest numbers of border interceptions and on‐shore detections of D. melanostictus were environmentally similar to locations within the species’ native range. Numbers of D. melanostictus interceptions and detections in Australia increased over time, but were unrelated to indices of air and maritime trade volume. Instead, numbers of interceptions and detections were determined by the country of origin of airplanes (Thailand) and ships (Indonesia). Thus, the common assumption that transport pressure is correlated with invasion risk does not hold in all cases. Our work builds on previous efforts to integrate transport pressure data and species distribution models, by jointly modelling the number of intercepted and detected stowaways, while incorporating imperfect detection and the environmental suitability of receiving hubs. The approach presented here can be applied to any system for which historical biosecurity data are available, and provides an efficient means to allocate quarantine and surveillance efforts to reduce the probability of alien species establishment.     

北京市典型公园外来入侵植物分布格局

近年来城市发展迅速,生境破碎化加剧,生物入侵的风险大大增加。外来入侵植物已入侵城市绿地生态系统,部分已成为城市公园生境中的优势种,占据本地植物生存空间、威胁本地植物生物多样性。为研究北京市公园外来入侵植物分布格局,以北京市4个不同功能区(核心区、拓展区、近郊区和远郊区)为研究区域进行外来入侵植物调查,基于19个典型公园的255个样方调查数据,对比不同功能区公园外来入侵植物组成和分布格局。调查共记录外来入侵植物40种,隶属于12科29属,其中菊科为优势科、一年生草本居多,牛膝菊(Galinsoga parviflora)和小蓬草(Erigeron canadensis)的频次和生态位宽度较大,分布较广泛,大狼杷草(Bidens frondose)和凹头苋(Amaranthus blitum)的优势度最大,资源竞争能力较强。外来入侵植物在拓展区公园的丰富度最高,核心区最低,对四个功能区的对比分析结果表明:(1)拓展区公园的外来入侵植物Shannon-Wiener多样性指数、丰富度和Pielou均匀度指数均显著高于核心区和远郊区,外来入侵植物Simpson指数则呈现出远郊区显著高于拓展区和近郊区的特征(P<0.05),本地植物则正好相反;(2)拓展区公园的外来入侵植物入侵强度系数(Invasion intensity index,III)最高,且显著高于核心区(P=0.008),其他功能区之间无显著差异;(3)核心区公园与其他三个区群落组成不同,其余三个功能区均较为相似。研究表明北京市公园外来入侵植物的丰富度除核心区以外整体上与城市化梯度呈正相关,核心区公园植物群落抵御外来入侵植物的能力较弱,拓展区公园植物群落中外来入侵植物丰富度高、分布均匀并处于优势地位,需及时治理。     

Determinants of plant species invasions in an arid island: evidence from Socotra Island (Yemen)

Understanding the factors which affect the distribution of alien plants in arid islands is complicated by the complex and stochastic nature of the invasion process per se, the harsh environmental conditions, and the low number of researchers and sampling effort. We present the results of the most comprehensive inventory to date of alien vascular plant species occurring in Socotra Island, a global biodiversity hotspot just beginning to be developed. A floristic survey was conducted between 2006 and 2008 in 36 grid cells of 10?×?10?km. We integrated this data from this survey with those from scientific literature. We recorded 88 alien plant species. Tree and herbaceous species were the most common growth forms. Species from Asia and edible species were prevalent. We identified 80 species considered weeds worldwide with >50?% adapted to arid conditions. We used a two-part model to analyze the spatial distribution of naturalized and alien plant species in relation to environmental and anthropogenic factors. Altitude and human-related factors play a significant role in the distribution of both naturalized and invasive species. Notably, the latter can potentially spread mainly in the alluvial basal areas. This study underpins the knowledge about alien species and their spatial distribution in Socotra Island. It provides a baseline for plant invasion management and contributes data for the analyses of invasion processes on islands worldwide.     

Monitoring and modeling the invasion of the fast spreading alien Senecio inaequidens DC. in an alpine region

We modeled the distribution of the South African alien Senecio inaequidens DC. in the Aosta Valley, Western Italian Alps, using data extracted from the Regional floristic database and from an intensive field survey carried out in years 2009–2010. The aims of the work were (1) to evaluate whether the species is in the introduction, colonization, or establishment stage of invasion, (2) to detect the environmental factors that drive the invasion process, and (3) to highlight the potential range of distribution of the alien species. The modeling framework was a stepwise generalized linear model (GLM), using gridded presence/absence data and environmental predictors such as topography, climate, land use, and anthropogenic and natural disturbances. GLM were fit both with and without an additional independent variable to take into account current dispersal limitations. S. inaequidens displayed a very fast spread in the Aosta Valley in the years 1990–2010. The species was positively associated with roads and rivers, southern slopes, and negatively with elevation. However, it was found at an elevation of 1600 m, showing the ability to reach higher elevations than those observed for other invasive alien species, and confirming to be pre-adapted to mountain conditions. The difference between the species distribution models, with and without dispersal constraints, suggested that the availability of seed sources still limits the potential distribution of the species, rather than the environmental variables, and that the realized regional niche differs to a great extent from the equilibrium niche. When limitations to the seed source cease (i.e., in the establishment stage), the species will likely invade large areas that are currently characterized by pastures and grasslands with native species of high agricultural importance. The invasion of S. inaequidens should therefore be considered a serious threat, due to its potential to invade mountain regions, and in particular to colonize habitats used for grazing and forage, thus leading to a high risk for cattle and human health. We discuss the relevance of the results both concerning communication with the public and to support local eradication and control activities. The inclusion of S. inaequidens in the “black list” of the regional law for the conservation of alpine flora (L.R. 45/2009) will help to transfer the information and support invasion control, in particular at medium elevations.     

Abundance and Distribution of Native and Alien Grasses in a “Cerrado” (Brazilian Savanna) Biological Reserve1

Several species of African grasses brought to Brazil as cattle forage have spread widely, outcompeting native herb species. The open forms of Brazilian savanna (“campo cerrado” and “campo sujo”) are the most affected by such invasions, because their structure is open, permitting enough sunlight into the lower strata. The invasion of alien forage grasses occurs in almost every cerrado nature reserve. This study was carried out in the “Cerrado de Hmas Biological Reserve”, Pirassununga, São Paulo State, Brazil, with the following objectives: (a) to compare the abundance of native and alien grass species; (b) to verify the importance of such alien grasses in the community; (c) to identity distribution patterns for the alien grass species in a gradient from the edge (highly disturbed) to the center (less disturbed) of the reserve; and (d) to explore the distribution of native and alien grasses in the search for possible competitive interactions. Using the “point method,” a total of 260 points was sampled and 52 species were recorded. The four most frequent species (FA = absolute frequency) were two native (Echinolaena inflexa [Poir.J Chase [FA = 38.85%] and Diandrostachya chrysotrix [Nees] Jacues Felix [FA = 15.38%]) and two alien African species (Melinis minutiflora Beauv. [FA = 33.08%] and Brachiaria decumbens Stapf [FA = 13.85%]). M. minutiflora and E. inflexa had higher values of absolute vigor (67.69 and 59.62%, respectively), relative vigor (28.16 and 24.80%, respectively), and cover (100.77 and 98.47, respectively), indicating higher biomasses and densities and their dominance in the community. B. decumbens presented the highest number of contacts per point, showing the highest stratification. To detect possible edge–center distribution gradients, correspondence analysis was done, initially using all the recorded species and subsequently only the four more frequent grasses, with similar results: (a) the alien grasses, especially M. minutiflora, did not show a distinct distribution gradient from edge to center, but occurred over the whole reserve; (b) no distinct ecotonal band around the reserve (edge–belt) was detected, the whole reserve seeming to be “ecotonal”; and (c) E. inflexa and M. minutiflora showed similar phytosociological patterns, and spatial distribution; association between these two species was statistically significant.     

Making environmental DNA count

The arc of reception for a new technology or method – like the reception of new information itself – can pass through predictable stages, with audiences’ responses evolving from ‘I don't believe it’, through ‘well, maybe’ to ‘yes, everyone knows that’ to, finally, ‘old news’. The idea that one can sample a volume of water, sequence DNA out of it, and report what species are living nearby has experienced roughly this series of responses among biologists, beginning with the microbial biologists who developed genetic techniques to reveal the unseen microbiome. ‘Macrobial’ biologists and ecologists – those accustomed to dealing with species they can see and count – have been slower to adopt such molecular survey techniques, in part because of the uncertain relationship between the number of recovered DNA sequences and the abundance of whole organisms in the sampled environment. In this issue of Molecular Ecology Resources, Evans et al. ( 2015 ) quantify this relationship for a suite of nine vertebrate species consisting of eight fish and one amphibian. Having detected all of the species present with a molecular toolbox of six primer sets, they consistently find DNA abundances are associated with species’ biomasses. The strength and slope of this association vary for each species and each primer set – further evidence that there is no universal parameter linking recovered DNA to species abundance – but Evans and colleagues take a significant step towards being able to answer the next question audiences tend to ask: ‘Yes, but how many are there?’     

Alien flora of mountains: global comparisons for the development of local preventive measures against plant invasions

Aim We use data from 13 mountain regions and surrounding lowland areas to identify (1) the origins, traits and cultural uses of alien plant species that establish in mountains, (2) the alien species that are most likely to be a threat and (3) how managers might use this information to prevent further invasions. Location Australia, Canada, Chile, India, New Zealand, South Africa, Spain, Switzerland, USA. Methods Lists of alien species were compiled for mountains and their surrounding or nearby lowlands. Principal co‐ordinates analysis was performed on a matrix of similarities created using presence/absence data for alien species. The significance of differences between means for (1) similarity metrics of lowland and mountain groups and (2) species traits of lowland and mountain alien floras was determined using t‐tests. In seven of the 13 mountain regions, lists of alien species undergoing management were compiled. The significance of differences between proportions of traits for species requiring and not requiring management input was determined with chi‐square tests. Results We found that the proximal lowland alien flora is the main determinant of a mountain region’s alien species composition. The highest similarities between mountain floras were in the Americas/Pacific Region. The majority of alien species commonly found in mountains have agricultural origins and are of little concern to land managers. Woody species and those used for ornamental purposes will often pose the greatest threat. Main conclusions Given the documented potential threat of alien species invading mountains, we advise natural resource managers to take preventive measures against the risk of alien plant invasion in mountains. A strategy for prevention should extend to the surrounding lowland areas and in particular regulate the introduction of species that are already of management concern in other mountains as well as climatically pre‐adapted alien mountain plants. These may well become more problematic than the majority of alien plants currently in mountains.